Refraction Flashcards
What is refraction
Change in direction of propagation of a wave due to a change in its transmission medium
Are internal angles within parallel-sided mediums equal
yes
Are incident and emergent angle equal if incident and emergent medium are the same?
yes
What is Snell’s law (law of refraction)
nsin = n’ sin’
= incident angle
’ = refracted angle
What is lateral displacement
Perpendiuclar distance between incident and emerging ray after traveling through parallel sided interfaces
What is apparent posistion/ thickness
Apparent posititon (img) differs from actual posistion (obj) when object from one medium is viewed from another medium
Apparent depth/ thickness of parallel sided plate viewed normal to its surface
what will the apparent position be when viewing from lower to higher index
Apparent posistion closer
What is apparent longitudnal displacement
apparent posistion of object viewed normally though parallel-sided plate surrounded by same medium
What is apica angle
angle between two refracting surfaces (at the apex, the tip of prism where two refracting surfaces meet)
What is the deviation of a prism
angular bending incident ray undergoes after refraction through prism
increases as apica angle increases
What does a larger deviation mean
More bending of incident light, higher prismatic power
What is normal incidence
When incident ray strikes prism perpendicular to the first refracting surface
incident angle = 0
what is normal emergence
Emergent ray leaves prism perpendicular to second refracting surface
emergent angle = 0
What is the criteria to be a ophthalmic prism
Apica angle lens than 15 degres
Either incident or emergent ray eaves normal to the surface
What does one prism dioptre mean (not as impt)
deviation that yields lateral displacement of 1cm at 1m
What is chromatic dispersion (not as impt)
Deviation of different wavelength varies as refractive index differs
- incident white spreads out its component colours, add colour fringes around object view thr prism
- distorsions
What is the most impt thing to rmb abt a prism?
Img always forms towards apex
What is the functional prescription to people with different types of tropia
Esotropia (in)
- base out
Exotropia (out)
- base in
Hypertropia (up)
- base down
Hypotropia (down)
- base up
how to rmb: point the top of foot to the direction n see what direction the back of your foot is pointing towards
What is the cosmetic prescription of people with different types of tropia
Esotropia
- base in
Exotropia
- base out
Hypertropia
- base up
Hypo tropai
- base down
How to rmb: opp. to functional
